Streptomycetes in Indoor Environments - Pcr Based Detection and Diversity

Streptomycetes are a group of environmental bacteria present in almost all kinds of environments. They are common in soil, but also found in sediments, composts and fodder, aquatic habitats, and buildings. In buildings they have been associated with moisture conditions that enable microbial growth, and thus, considered as indicators of moisture and microbial damage. Streptomycetes are also potent inducers of inflammatory responses in vitro and in vivo and therefore, possible causes of adverse health effects in moisture damaged buildings. A PCR based detection method was applied and tested with soil, building material and dust samples. According to the current sequence information, the PCR primers were specific for streptomycetes. The method proved to be specific also in experiments using potentially interfering microbes and environmental samples as template DNA. The results were confirmed by sequencing. Streptomycetes were detected in 81 % of the dust samples (N=47) by PCR and mesophilic actinomycetes in 36 % of the samples by culture. The results of culture and PCR did not correlate well with each other, which may have several reasons. The amount of negative samples was higher by culture, indicating that the sensitivity of the method is poorer. The slow-growing streptomycetes were probably overgrown by other microbes and remained undetected. PCR amplification may have been affected by inhibiting agents present in environmental samples and co-purified with DNA. The amount of streptomycete -specific PCR amplification product was higher in dust samples collected from moisture-damaged houses than in dust from non-damaged residences (p < 0.05, Mann-Whitney test). The diversity of streptomycetes in indoor environments was investigated by characterising Streptomyces strains isolated from indoor air (N=9), building materials (N=2), and house dust (N=15) by 16S rDNA sequencing. In a phylogenetic tree, the majority of these strains (16) affiliated with the Streptomyces griseus –cluster, which is the largest cluster of the genus, inhabiting many secondary metabolite-producing species. Another four strains grouped with members of the Streptomyces albidoflavus –cluster and a third group affiliated with Streptomyces cyaneus and with the model actinomycete Streptomyces coelicolor A3(2). Two isolates showed no clear affiliation to known sequences. The results of a culture-independent approach, which included direct PCR amplification of the 16S rDNA from template DNA isolated from building materials, sequencing and sequence analysis, revealed that these sequences generally clustered with the same species than cultured strains. However, a somewhat broader diversity was detected indicating that this approach could be useful for detecting strains that are not easily cultured.